The present invention is directed towards graphical indicators for use in visual displays/view finders and more particularly, to aid in surveying stakeout operations executed in conjunction with angular and range measuring surveying devices.
In the field of surveying, stakeout operations normally involve the marking on the grounds of points or areas of specific interest such as boundary intersections, roads, access points for utilities and so forth. Stakeout operations are normally undertaken by two operators, one of whom operates a surveying optical instrument at a fixed reference point, while the other operator is mobile and is equipped with a surveying range pole or similar appropriate device. The optical instrument is capable of accurately determining vertical and horizontal angles and often incorporates an integral Electronic Distance Measuring (EDM) device capable of measuring distances co-axially along the optical axis of the optical instrument. The exact terrestrial location of the fixed reference point where the optical instrument is sited, is (unless already known) first required to be established. This may be achieved by conventional surveying techniques or as is now becoming commonplace, by use of a Global Positioning System (GPS) receiver. The GPS receiver utilizes signals emanating from an orbiting constellation of GPS satellites to calculate its position by known means. The location of the fixed reference point (the xe2x80x98survey sitexe2x80x99) may be expressed in terms of any suitable frame of reference, such as the standard GPS reference ellipsoid WGS-84, or (by means of the appropriate transformation) a convenient local system. The stakeout sites may also be defined with respect to the same reference systems or simply by their relative distance and angular orientation from the survey site. The stakeout sites are stored in a data collection and calculation means (referred to as a data collector) which can be integrated into the GPS receiver and/or the optical instruments. The GPS receiver/data collector is linked electronically with the optical instrument, thus permitting either device to display the measurements made by one or both devices.
Once the location of the survey site has been established, the distance and angle to the first stakeout site is calculated and displayed by the GPS data collector/optical instrument. The optical instrument operator (herein termed the xe2x80x98instrument operatorxe2x80x99) then directs the second operator by means of suitable signals to move the range pole in the direction and for the distance calculated. After each corrective movement of the range pole, the optical instrument is realigned aligned with the range pole and a distance measurement is effected and recorded, whereupon the data collection/calculation means calculates the new error distance between the current range pole location and the stakeout point. The error distance, (normally expressed as mutually perpendicular components e.g. left, right, in, out with respect to the instrument operator) is conveyed to the second operator as movement instructions, by hand signals, orally or by radio. This iterative procedure is repeated until the error distance between the range pole location and the stakeout site falls within the tolerance threshold specified by the operator and a stake or similar is used to mark the location. In practice, once the optical instrument is aligned at the correct horizontal angle (i.e., the instrument is xe2x80x98on-linexe2x80x99), normally, only the error distance along the axis between the optical instrument and the stakeout site requires measuring and correcting.
The instrument operator is reliant on the numerical values displayed by the data collector to guide the second operator to the stakeout point and whilst this provides an acceptable result, the speed and efficiency of the above process could be enhanced by the use of suitable visual aids. The human mind is far more receptive to visual cues than alpha-numeric data as a means of executing or instructing specific movements, i.e., guiding the operator and range pole to the stakeout point.
Such visual aids are employed in several position-related applications, such as marine radar and/or GPS displays, wherein the desired course and the actual course are often represented from a third-angle view-point, simulating a three-dimensional perspective. Graphical; symbols are used to denote various factors such as the cross-track course error and the correction required to bring the vessel on course. However, marine-related applications are naturally uninterested in the elevation of the craft and the degree of positional accuracy required is much lower than for surveying purposes.
Such displays typically display range and bearing to a single remote point of interest (e.g. a way-point, harbor, or a hazard of some type), with the aforementioned course correction indication being used to show the action necessary for the user to converge (or avoid, in the case of a hazard) on the same single remote point, i.e., the corrective movement is undertaken by the user/observer and not at the observed/measured remote location.
In contrast, during surveying stakeout operations, the user (the surveyor) is located at a single fixed location and it is a second mobile object (i.e., the range pole held by the second operator) that requires corrective guidance instructions to converge on a; predetermined remote location (the stakeout site). There is thus a subtle though fundamental conceptual and practical difference between the needs and implementation of marine radar type displays and those of a surveying instrument/system used for staking-out.
The use of graphical cues to align/orientate an object such as a surveyor""s optical instrument and to direct the movement of a third party or object such as a range pole, would reduce the activity execution time, thus reducing costs and attenuate errors such as the transposition of figures and/or the correct direction of corrective movement.
In one embodiment, the present invention provides a method and apparatus configured to provide: graphical symbols indicative of a separation value between a first and second location, measured from a predetermined reference point, wherein said separation value relates to at least one of:
(i) the direct distance between said first and second locations and
(ii) the angle subtended between said first and second location at the said predetermined reference point.
The said separation value may be resolved into mutually orthogonal components. The present invention may also includes an alpha-numeric display configured to represent the magnitude of said separation values.
In one embodiment, the graphical symbols include two pairs of opposed arrows orientated vertically and horizontally respectively, denoting the corresponding said separation value component. The arrows point towards a center graphical element (representing either the first or second location) from the location of the other of the first or second location, as seen from the perspective of said predetermined reference point.
If the corresponding separation value component exceeds a predetermined threshold value, a single arrow of either said pair of arrows is displayed. Both arrows of either pair of arrows are simultaneously displayed when the corresponding separation value component is less than said predetermined threshold value. The magnitude of each said separation value and component may be displayed in alpha-numeric form adjacent to each corresponding graphical symbol/arrow.